Abstract: On the Relevance of Upscaling to Petroleum Migration in Basin Modeling

Bender, A. A.; Aguiar, L. A. M.; Andrade, D. E. - Petrobras/Cenpes

The quantification of the processes involved in basin modeling studies have progressed considerably in the last 20 years. The main processes are related to hydrocarbon generation, expulsion and secondary migration and their quantification is considerably complex given the changes a basin experiences during its evolution. For exploration purpose, the focus of basin modeling is on the large scale, in which the size of the sections are typically 10's to 100's km. Because of the large amount of data required to carry out a simulation of this range of magnitude, the input of data has been simplistic. Some studies are built in a way that large number of layers are represented nearby boreholes but, where the boreholes are lacking, the input of data is at the cartoon level. Based on the published literature, an understanding of the adequate spatial representation of sedimentary layers in basin modeling studies is lacking. In this context, extrapolation and interpolation of data between boreholes are necessary. We emphasize the need to integrate well with seismic data in order to build a model in a continuous and more consistent manner. There are several reasons that allow this approach to be practical and they include ready access to seismic and well database, inversion routines, availability of powerful machines, and easy-to-use software. An integration of well and seismic data in a 2D (not to mention 3D) simulation obviously involves large number of details, consequently this "realistic" approach is a dangerous trap. An upscaling scheme is necessary to reduce man and machine power and, by this way, to make this approach feasible.

Our objective is to discuss the adequate spatial representation of sedimentary layers and its effect on the fluid migration along a geological section of the Brazilian passive margin. To reach this objective we integrate well and seismic data in order to get, as complete as possible, lithological and petrophysical information of one section. Based on this section, we produce three upscaled versions of it. The first one is not actually upscaled but rather built in a traditional way, with large domains containing average petrophysical properties. The second and third sections were built with an integrated approach and were upscaled to an intermediate and small length scale level. The integrated approach uses lithological and porosity information extracted from seismic data, calibrated with well data, as input to the Temispack program. Although this integration is already a significant achievement, the upscaling scheme for this kind of study cannot be borrowed directly from reservoir studies. This paper presents a work under progress but our preliminary results are indicative of the importance of splitting the geological section in homogeneous domains. Additionally, we emphasize the need of preserving the more permeable domains, even if they consist of thin layers because they play an important role on the direction of secondary migration.

AAPG Search and Discovery Article #90933©1998 ABGP/AAPG International Conference and Exhibition, Rio de Janeiro, Brazil